scholarly journals Stimulatory effect of arginine on acetylglutamate synthesis in isolated mitochondria of mouse and rat liver

1985 ◽  
Vol 232 (2) ◽  
pp. 329-334 ◽  
Author(s):  
S Kawamoto ◽  
T Sonoda ◽  
A Ohtake ◽  
M Tatibana
Keyword(s):  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Carbamoyl Phosphate ◽  
Isolated Mitochondria ◽  
Significant Difference ◽  
Glutamate Synthesis ◽  
Arginine Concentration ◽  
Allosteric Activator

N-Acetyl-L-glutamate synthetase (EC 2.3.1.1) catalyses the synthesis of N-acetyl-L-glutamate, an allosteric activator of carbamoyl-phosphate synthetase I in the liver of ureotelic animals, and the first enzyme is activated specifically by arginine. We have proposed that arginine can stimulate acetylglutamine synthetase in vivo and thereby increase the mitochondrial content of acetylglutamate. The effects of arginine on acetylglutamate synthesis in isolated mitochondria were investigated in detail in the present work. When rat liver mitochondria were isolated and incubated with [14C]glutamate and unlabelled acetate as substrates, acetyl[14C]glutamate synthesis in the mitochondria was more extensive in the presence than in the absence of L-arginine. There was no significant difference between the specific radioactivities of intramitochondrial [14C]glutamate in the presence and absence of arginine. When rat liver mitochondria were incubated with [14C]acetate and unlabelled glutamate as substrates, arginine also stimulated acetyl[14C]glutamate synthesis in the isolated mitochondria. L-Lysine or L-homoarginine, which does not activate acetylglutamate synthetase, had no effect on acetylglutamate synthesis, in the isolated mitochondria. The arginine concentration giving half-maximal synthesis of acetylglutamate in isolated mitochondria was about 50 microM, which is in the range of physiological concentrations of arginine in the liver. As we previously reported [Kawamoto, Ishida, Mori & Tatibana (1982) Eur. J. Biochem. 123, 637-641], the sensitivity of acetylglutamate synthetase to arginine activation undergoes marked changes after food ingestion. The extent of arginine activation of acetylglutamate synthesis in isolated mitochondria correlated well with the sensitivity of acetylglutamate synthetase extracted from the mitochondria to arginine activation. These data lend further support to the idea that arginine itself activates the mitochondrial synthesis of acetylglutamate.

Evidence for the Biosynthetic Difference between Isolated Mitochondria and Microsomes from Guinea-Pig and Rat Liver Regarding Lysophospharidic Acid, Phosphatidic Acid, CDP-Diglyceride, Phosphatidylglycerol, and Cardiolipin

1974 ◽  
Vol 52 (10) ◽  
pp. 936-939 ◽  
Author(s):  
J. B. Davidson ◽  
N. Z. Stanacev
Keyword(s):  
Guinea Pig ◽  
Phosphatidic Acid ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Marker Enzymes ◽  
Synthetic Enzymes ◽  
Isolated Mitochondria ◽  
Significant Difference ◽  
Nadph Cytochrome C Reductase

The enzymatic activities of marker enzymes (NADPH – cytochrome c reductase and glucose-6-phosphatase) and synthetic enzymes (acyl-CoA:sn-glycero-3-phosphate acyltransferase, CTP:sn-3-phosphatidic acid cytidyltransferase, and CDP-diglyceride:sn-glycero-3-phosphate phosphatidyltransferase) were measured in both isolated mitochondria and microsomes from liver of guinea pig and rat. Results thus obtained show a significant difference in activities of these enzymes between subcellular particles within species and between two examined species. The activity of acyl-CoA:glycero-3-phosphate acyltransferase in guinea-pig mitochondria parallels the activity of microsomal marker enzymes in this fraction, while in rat liver mitochondria the activity is relatively higher and cannot be accounted for by the microsomal content as determined by marker enzymes. Implications of these results regarding mitochondrial autonomy in the biosynthesis of polyglycero-phosphatides and their precursors are discussed.

scholarly journals Protein-mediated uptake of vitamin B12 by isolated mitochondria

Blood ◽  
1976 ◽  
Vol 47 (6) ◽  
pp. 923-930 ◽  
Author(s):  
RA Gams ◽  
EM Ryel ◽  
F Ostroy
Keyword(s):  
Vitamin B12 ◽  
Rat Liver ◽  
Mitochondrial Respiration ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Isolated Rat Liver ◽  
Isolated Mitochondria ◽  
Isolated Rat

Abstract Protein-mediated B12 uptake by isolated rat liver mitochondria has been shown to be enhanced by plasma transcobalamin (TC-II) but not by salivary R binder in vitro. The process is enhanced by calcium and depends on active mitochondrial respiration. Following uptake, cyanocobalamin is converted to adenosyl and methylcobalamins and released from the mitochondria. TC-II appears to be required for both cellular and mitochondrial uptake of vitamin B12.

Import of the glucocorticoid receptor into rat liver mitochondria in vivo and in vitro

1993 ◽  
Vol 46 (3) ◽  
pp. 401-413 ◽  
Author(s):  
C. Demonacos ◽  
N.C. Tsawdaroglou ◽  
R. Djordjevic-Markovic ◽  
M. Papalopoulou ◽  
V. Galanopoulos ◽  
...  
Keyword(s):  
Glucocorticoid Receptor ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria

scholarly journals Stable enhancement of calcium retention in mitochondria isolated from rat liver after the administration of glucagon to the intact animal

1978 ◽  
Vol 176 (3) ◽  
pp. 705-714 ◽  
Author(s):  
Veronica Prpić ◽  
Terry L. Spencer ◽  
Fyfe L. Bygrave
Keyword(s):  
Rat Liver ◽  
Molecular Mechanisms ◽  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Mitochondrial Protein ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Matrix Space ◽  
The Matrix

1. Mitochondria isolated from rat liver by centrifugation of the homogenate in buffered iso-osmotic sucrose at between 4000 and 8000g-min, 1h after the administration in vivo of 30μg of glucagon/100g body wt., retain Ca2+ for over 45min after its addition at 100nmol/mg of mitochondrial protein in the presence of 2mm-Pi. In similar experiments, but after the administration of saline (0.9% NaCl) in place of glucagon, Ca2+ is retained for 6–8min. The ability of glucagon to enhance Ca2+ retention is completely prevented by co-administration of 4.2mg of puromycin/100g body wt. 2. The resting rate of respiration after Ca2+ accumulation by mitochondria from glucagon-treated rats remains low by contrast with that from saline-treated rats. Respiration in the latter mitochondria increased markedly after the Ca2+ accumulation, reflecting the uncoupling action of the ion. 3. Concomitant with the enhanced retention of Ca2+ and low rates of resting respiration by mitochondria from glucagon-treated rats was an increased ability to retain endogenous adenine nucleotides. 4. An investigation of properties of mitochondria known to influence Ca2+ transport revealed a significantly higher concentration of adenine nucleotides but not of Pi in those from glucagon-treated rats. The membrane potential remained unchanged, but the transmembrane pH gradient increased by approx. 10mV, indicating increased alkalinity of the matrix space. 5. Depletion of endogenous adenine nucleotides by Pi treatment in mitochondria from both glucagon-treated and saline-treated rats led to a marked diminution in ability to retain Ca2+. The activity of the adenine nucleotide translocase was unaffected by glucagon treatment of rats in vivo. 6. Although the data are consistent with the argument that the Ca2+-translocation cycle in rat liver mitochondria is a target for glucagon action in vivo, they do not permit conclusions to be drawn about the molecular mechanisms involved in the glucagon-induced alteration to this cycle.

Effects of Glucagon Upon Rat Liver Mitochondria in Vivo

1974 ◽  
Vol 147 (3) ◽  
pp. 803-806 ◽  
Author(s):  
J. N. Williams ◽  
S. L. Thorp
Keyword(s):  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria

scholarly journals Effects of incubation at physiological temperatures on the concentration-dependence of [2-14C]malonyl-CoA binding to rat liver mitochondria

1985 ◽  
Vol 231 (2) ◽  
pp. 343-347 ◽  
Author(s):  
V A Zammit ◽  
C G Corstorphine
Keyword(s):  
Rat Liver ◽  
Specific Binding ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Temperature Dependent ◽  
Malonyl Coa ◽  
Saturation Kinetics ◽  
Different Temperatures ◽  
Cpt I

Specific binding of [2-14C] malonyl-CoA to rat liver mitochondria was measured at different temperatures and after various periods of time of exposure of the mitochondria to the ligand. Incubation of mitochondria at 37 degrees C in the absence of malonyl-CoA resulted in a decrease in their ability to bind malonyl-CoA at all concentrations tested (up to 55 microM). However, incubation of mitochondria in the presence of malonyl-CoA resulted in the loss of the binding only by a low-affinity component. By contrast, there was an increase in the binding that occurred at low, physiological, concentrations of malonyl-CoA. These differences in the response of the two binding components to incubation conditions were used to obtain quantitative data about their respective saturation kinetics. Evidence was obtained that, whereas the high-affinity component approached saturation hyperbolically with respect to malonyl-CoA concentration, the low-affinity component had sigmoidal characteristics. The concentrations of malonyl-CoA required to half-saturate the two components were 2-3 microM and 30 microM for the high- and low-affinity components respectively. Evidence was also obtained for the involvement of a temperature-dependent transition, that occurred at around 25 degrees C, in the modulation of malonyl-CoA binding to the mitochondria. The possible physiological roles of the two components of malonyl-CoA binding in relation to the regulation of overt carnitine palmitoyltransferase (CPT I) activity in vivo are discussed.

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